The degree of integration of integrated circuits has recently become much higher, and the processing of ultra-fine patterns having a line width of a quarter micron or below is required in the production of semiconductor substrate, for example, VSLI. It is known to make an exposure light source for use in the production of resist pattern shorter as one means for the formation of fine pattern.
For instance, in the production of semiconductor device having the degree of integration up to 64 Mbits, an i-line (365 nm) of high pressure mercury lamp has been employed as the light source. As a positive resist corresponding to the light source, a large number of compositions containing a novolak resin and a naphthoquinone diazide compound as a photosensitive substance have been developed. These compositions have achieved full success in the processing of linewidth up to about 0.3 μm. Also, in the production of semiconductor device having the degree of integration of 256 Mbits or more, a KrF excimer laser beam (248 nm) is employed as the light source in place of the i-line.
In recent years, for the purpose of the production of semiconductor device having the degree of integration of 1 Gbit or more, as a light source having shorter wavelength, the use of an ArF excimer laser beam (193 nm) and further, the use of an F2 excimer laser beam (157 nm) in order to form a pattern of not more than 0.1 μm have been investigated.
In response to such a trend of using light source having a shorter wavelength, constituents of the resist materials and structure of compounds used for the constituents have been greatly changed. Specifically, since the conventional resist material containing a novolak resin and a naphthoquinone diazide compound has a large absorption in a far ultraviolet region of around 248 nm, it is hard for the exposure light to adequately reach to the bottom of resist layer. As a result, the resist material has low sensitivity and can merely provide a tapered pattern.
In order to resolve such problems, a composition in which a resin including a basic skeleton of poly (hydroxystyrene) that has a small absorption in the region of around 248 nm and being protected by an acid-decomposable group is used as the main component and a compound that generates an acid upon irradiation of a far ultraviolet ray (a photo-acid generator) is used in combination, that is a so-called chemical amplification resist has been developed. The chemical amplification resist has high sensitivity and can form a pattern of high resolution because the solubility thereof in a developer is changed by a catalytic decomposition reaction of an acid generated in the irradiated area.
However, in case of using an ArF excimer laser beam (193 nm), the above-described chemical amplification resist is still in sufficient for providing satisfactory performances since a compound containing an aromatic group essentially has a large absorption in the region of around 193 nm.
In order to solve the problem, improvement of the chemical amplification resist has been made by replacing the acid-decomposable resin including a basic skeleton of poly (hydroxystyrene) with an acid-decomposable resin in which an alicyclic structure that does not have an absorption in the region of around 193 nm is introduced into the main chain or side chain thereof.
It has been found in case of using an F2 excimer laser beam (157 nm), however, that since the above-described alicyclic group-containing resin still has a large absorption in the region of around 157 nm, it is insufficient for obtaining the desired pattern of not more than 0.1 μm. In the circumstances, it is reported that a resin having a fluorine atom (a perfluoro structure) introduced therein has sufficient transparency in the region of around 157 nm in Proc. SPIE., Vol. 3678, Page 13 (1999). Structures of effective fluorine resins are also proposed, for example, in Proc. SPIE., Vol. 3999, page 330 (2000), ibid., page 357 (2000), ibid., page 365 (2000) and WO 00/17712.
However, a resist containing such a fluorine resin is not always satisfactory with respect to dry etching resistance. It is also desired to improve a coating property (uniformity of coated surface) caused by the unique water-repellent and oil-repellent properties due to the perfluoro structure and to prevent development defect.
Further, when the resolution of lithography comes close to the limit in accordance with the miniaturization of processing size of pattern, it is difficult to ensure sufficient defocus latitude. Thus, a resist having a broad defocus latitude has been desired. The term “resist having a broad defocus latitude” means a resist in which variation of linewidth based on the defocus is small.
Moreover, when a contrast of image formation becomes poor in accordance with the miniaturization of processing size of pattern, a boundary region between the exposed area and the unexposed area becomes fuzzy and uniformity of edge of line pattern (line edge roughness) remarkably gets worth. Thus, solution of such a problem has also been desired.